Which of the following statements are correct?

(A) The electronic configuration of Cr is [Ar] 3d⁵ 4s¹.

(B) The magnetic quantum number may have a negative value.

(C) In the ground state of an atom, the orbitals are filled in order of their increasing energies.

(D) The total number of nodes are given by n $$-$$ 2.

Choose the most appropriate answer from the options given below :

The solubility of AgCl will be maximum in which of the following?

The electronic configuration of Pt (atomic number 78) is :

Two isomers 'A' and 'B' with molecular formula C₄H₈ give different products on oxidation with KMnO₄ in acidic medium. Isomer 'A' on reaction with KMnO₄/H⁺ results in effervescence of a gas and gives ketone. The compound 'A' is